On a serious note, if Justice League doesn't break a billion, I would personally consider it a pretty epic failure, all things considered. It has the DC big three, and not only has Wonder Woman been doing well, but the superhero films in general have been good this year so far (GotG 2, Logan and Spiderman as well), which will likely have a positive influence on audience willingness to shill out money for this. And the CW shows have made characters like the Flash much more visible and popular among more mainstream audiences. So, one would expect it to at least make a billion at the box office.